Thin films of (CoCrCuFeNi) were deposited by direct current reactive magnetron sputtering. Two different targets were used. Thin films deposited from a solid near-equimolar target showed a Cu excess with segregation of Cu in the film resulting in the formation of a nanocomposite film. It was also not possible to reach fully stoichiometric nitride thin films with this target. To overcome this problem, a powder target with adjusted composition was used in a second series of experiments. As derived from longitudinal and transversal sound velocity measurements, a transition from the metallic face-centred cubic lattice to the nitride B1 (NaCl) structure is observed. The observed transition corresponds with the process change from the metallic regime at low nitrogen partial pressure to the poisoned regime at high nitrogen partial pressure. TEM measurements show a typical zone T growth with a strong (100) texture in the nitride regime, and reveal a mixing of the constituent metals at the nanometer scale. This study demonstrates that the constituent metals do not form binary nitrides, but a complex nitride is formed.